Back rivet set on rudder trailing edge

[BoilerFlyer]

I've come to the rudder trailing edge rivet portion of our program and I must say, I want to start by thanking everyone for their amazing posts here on this topic already! It has been incredibly helpful, but there is one topic that I can't seem to find any information on. So far I have put in about 6 rivets using the angle iron method popularized all over and I'm incredibly happy with the end results with one incredibly large exception: I'm afraid the back rivet set is damaging my rudder skin. I can see the impact circles being left on the skin. I have tried to vary the pressure in my gun to the point of almost making it unusable it is so low (Van's recommends a 3 second total drive time in the manual) to high enough I cut that 3 seconds down to just over 1. Same result regardless of pressure - impact rings on the trailing edge.

Thoughts? How have people handled this?

 

[leok]

you should be using a mushroom flush set angled to match the skin surface.

I found it helpful to partially squeeze the rivets with a hand squeezer, and then come back and hit them with the gun to finish.